"Mark Rand" wrote in message
...
On Thu, 26 Nov 2009 13:22:11 -0500, "Ed Huntress"

wrote:



Ok, and thanks for the references. For the moment, I'd like to get
straight
in my mind how this Hardinge spindle works. Maybe I can cut to the chase
by
asking a couple of questions, since you have the drawing and may be able
to
see the details with it.

A lathe spindle has to deal with four forces. First, the major radial
load,
which usually is taken out by the front (spindle-nose-end) bearing.
Second,
the minor radial load, which typically is the tail-end bearing. The ones
I'm
questioning here are the other two: the thrust loads in each direction --
Z+
and Z-.

Which bearing takes out each of these two thrust loads? How far apart are
the front and rear bearings? Are they both single-row types, or is one a
double-row? Finally, do either of the bearings have a split race?

Thanks.

AFAICT, the HLV-H has two identical angular contact bearings spaced a long
way
apart with a spacer on the mandrel for the inner races and external
clamping
for the outer races. I believe they are back-to-back rather than
face-to-face,
but could be wrong.

The HLV has a pair of the same bearings as above back-to-back at the
front.
clamped together by the outer races and a deep groove ball bearing at the
rear
floating in a bore, but lightly loaded with a wave washer.


The HLV-H design is better than the HLV.

The HLV has a number of gearbox shafts with three bearings fighting
against
each other. This results in the fitted C1 bearings coming out more sloppy
than
C3 after a few decades. The headstock bearings are much more expensive
than
6200C1s though. I don't know if the HLV-H has these problems.


Mark Rand
RTFM

Ho-kay. Now, the reputation of Hardinge toolroom lathes is that the spindle
typically gets up to about body temperature or slightly above when they're
running and stabilized (this is second-hand info; I've never put my hand on
one). That's quite cool, but not out of reason for near-perfect bearings.

Apologies for doing this all in Fahrenheit and inch measurements, but if the
bearings are separated by, say, 8 inches, the spindle (and the spacer,
assuming it's steel) between them will expand by just under 0.002 in. with a
30 deg. F rise in temperature. (Steel expands at 7.3 x 10^-6 inch per inch,
per degree F, if anyone cares to check my calculations).

How do they cope with that? Does the headstock casting supposedly compensate
perfectly for that growth? Because 0.002 in. is enough to completely unload
any preloaded, high-quality bearings -- or to destroy them if they're each
facing the other way.

--
Ed Huntress